1. Field of the Invention
The present invention relates to a human-machine interface apparatus with expanded function, especially to a human-machine interface apparatus using an expansion interface and at least one external key unit to expand the input function thereof.
2. Description of Related Art
Human-machine interface devices are omnipresent in modern world as the progress and prevailing of electronic technology. For example, people often use human-machine interface devices for ATM, parking lot and factory to facilitate the transaction, payment and machine operation. The human-machine interface device generally comprises input interfaces and output interfaces. The input interface can be simply implemented with a plurality of keys, a keyboard or other kinds of input units such as a touch pad. The output interface can be simply implemented with a plurality of indication lamps, or seven-segments display or a complicated LCD for text and graphic display.
The human-machine interface devices for industrial applications can be roughly classified into two types, namely, keyboard type and touch pad type. The touch-pad-type human-machine interface devices have the advantages of flexible definition of input function. The input function can be re-defined by changing the displayed graphic icon. However, the touch-pad-type human-machine interface devices have higher cost. The keyboard-type human-machine interface devices (or referred to as non touch-pad-type human-machine interface devices) generally comprises a plurality of function keys and numeral keys for input function, and further comprises a relatively smaller LCD screen for display. The non touch-pad-type human-machine interface devices have the advantage of low cost, however, the key input function thereof is difficult to redefine on key per se. The key input function thereof may be redefined by change the displayed icon on screen. However, the non touch-pad-type human-machine interface device generally has relatively smaller LCD screen, it is inconvenient for user.
FIG. 1A shows a conventional non touch-pad-type human-machine interface device 10, which comprises a relatively smaller LCD screen 100, a function key set 110 (such as F1, F2 function key etc.) and a direction key set 120 (such as Upper, Down, Right and Left direction keys). The legend of the key is difficult to amend even thought the function thereof is redefined. It is also inconvenient for user because the keys are usually small and hard to operate. FIG. 1B shows another conventional non touch-pad-type human-machine interface device 20, which comprises an LCD screen 200, a function key set 210 (such as F1, F2 function key etc.), a direction key set 220 (such as Upper, Down, Right and Left direction keys) and a keypad 230 for inputting numeral digits. This non touch-pad-type human-machine interface device 20 has larger size than that shown in FIG. 1A. Moreover, the legend of the key may be amended by replacing a nameplate (not shown) associated with the key. Therefore the legend of the key can be changed to other command such as Run, or Stop, Forward, Backward after the key function is redefined. However, the nameplate is tended to degrade by moisture and the provision of new nameplate will increase cost.